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Dearomatizing spirocyclization reactions are very appealing synthetic strategies to generate functionalized three-dimensional scaffolds from simple two-dimensional precursors. Recently, the field of transition-metal-catalyzed dearomatizing spirocyclization reactions of indolyl ynones has burgeoned, as the construction of synthetically challenging quaternary spirocyclic carbons is easily achieved. In this review, we introduce an overview of advances in the transition-metal-catalyzed dearomatizing spirocyclization reactions of indolyl ynones, with the reactions being categorized according to type of catalyst.

An efficient copper-catalyzed oxidative cyclization of diynes is described. A range of functionalized γ-lactams can be readily constructed by using this protocol. This copper-catalyzed oxidative process proceeds through an alkyne oxidation, carbene/alkyne metathesis, and donor–donor carbene oxidation sequence. The use of readily available substrates, high flexibility, a simple procedure, and mild reaction conditions render the procedure a viable alternative for the preparation of functionalized γ-lactams.

Described herein is a copper-catalyzed multifunctionalization of indolyl ynones, allowing the synthesis of dihalogen-substituted spiroindoles. This Cu catalysis is also applicable to the synthesis of cyclopenta[c]quinolin-3-ones via decarbonylation.

Catalyst-dependent oxidative cyclization of diynes with pyridine N-oxides is achieved using an amide directing group. Non-polarized and aminated alkyne could be selectively activated by copper and gold, thus leading to divergent synthesis of a range of pyrroles and dihydroindeno[1,2-c]pyrrol-3(2H)-ones. It should be noted that this difference might be attributed to the multicoordinated Cu center and the linearly aligned dicoordinated Au center.

In recent years, transition-metal-catalyzed tandem cyclization reactions of alkynes, especially those involving a metal carbene intermediate, have received worthwhile interest, as this type of reaction does not require the use of risky and potentially explosive diazo compounds as starting materials for carbene generation. A significant and general strategy for the stereospecific synthesis of 5-membered cycles is Nazarov cyclization based on the 4π-conrotatory electrocyclization of a conjugated pentadienyl cation to afford a cyclopentenyl cation. In this review, we introduce an overview of recent advances in the transition-metal-catalyzed Nazarov cyclization of alkynes via a metal carbene intermediate, and categorize these reactions according to the structure of the metal carbene. Our aim is to accelerate advancements in this enchanting area of research.

Energy filtering effect is usually utilized in composites to enhance the thermoelectric performance, and a reliable theoretical approach is needed to predict the optimum parameters related to this effect. By taking Bi2Te3 as an example, we show that first principles calculations and Boltzmann transport equations can be used to evaluate energy filtering effect, and the optimal values for the maximum power factor of interfacial potential barrier height (Eb) and carrier scattering probability (p) can be calculated precisely. The calculation results show that the power factor can be greatly enhanced at high carrier concentrations by energy filtering. This enhancement is sensitive to Eb and p: to achieve 40% power factor enhancement, Eb must be in the range 0.06–0.10 eV, and p should be greater than 60%. The optimal Eb also shows weak dependence on p. Our approach can be easily applied to other materials due to the generality of first principles calculations, and will aid high throughput screening for new thermoelectric composites.

Background The investigation of the genetic basis of local adaptation in non-model species is an interesting focus of evolutionary biologists and molecular ecologists. Identifying these adaptive genetic variabilities on the genome responsible can provide insight into the genetic mechanism of local adaptation. Results We investigated the spatial distribution of genetic variation in 22 natural populations of Pterocarya stenoptera across its distribution area in China to provide insights into the complex interplay between multiple environmental variables and adaptive genetic differentiation. The Bayesian analysis of population structure showed that the 22 populations of P. stenoptera were subdivided into two groups. Redundancy analysis demonstrated that this genetic differentiation was caused by the divergent selection of environmental difference. A total of 44 outlier loci were mutually identified by Arlequin and BayeScan, 43 of which were environment-associated loci (EAL). The results of latent factor mixed model analysis showed that solar radiation in June (Sr6), minimum temperature of the coldest month (Bio6), temperature seasonality (Bio4), and water vapor pressure in January (Wvp1) were associated with the highest numbers of EAL. Sr6 was associated with the ecological habitat of “prefered light”, and Bio6 and Wvp1 were associated with the ecological habitat of “warm and humid environment”. Conclusions Our results provided empirical evidence that environmental variables related to the ecological habitats of species play key roles in driving adaptive differentiation of species genome. Electronic supplementary material The online version of this article (10.1186/s12870-018-1524-x) contains supplementary material, which is available to authorized users.

Considering the important influence of the deposition pressure on the growth of thin films, such as deposition rate, crystalline volume fraction and density, etc., and based on the analysis of the advantages and disadvantages on the mono-pressure method, we proposed a new method of high- and low-pressure combination to prepare hydrogenated microcrystalline silicon (μc-Si:H) films, i.e. at first we used high pressure to deposit film in 2 min in order to minish the thickness of incubation layer from the amorphous phase transition to crystalline phase, and then used low pressure to deposit film in 18 min to improve the density and decrease the oxidation of the film. The experimental results showed that using this new method the thin film with high crystalline volume fraction of 61% and low light-induced degradation ratio of 5.6% at 210 min was obtained, and meanwhile, it also possessed higher density and better photoelectronic properties than mono-pressure method.

Perovskite phase SnTiO3 was predicted to have a large spontaneous polarization of 1.1 C/m2, but its synthesis has been unsuccessful so far. Here, we calculated the ferroelectric properties of a series of Ruddleson-Popper (RP) phase SnO(SnTiO3)n (n = 1 ∼ 6), with perovskite SnTiO3 as the ending structure (n = ∞), using the first principles calculations. An analysis of RP phase tolerance factor indicated that the fabrication of the RP phase SnO(SnTiO3)n may be easier than that for SnTiO3. For bulk SnO(SnTiO3)1, the most stable phase is Aba2 with a spontaneous polarization of 0.53 C/m2 along [110]. Aba2 is also the most stable phase for SnO(SnTiO3)1 under biaxial strain. For RP phase SnO(SnTiO3)n on a SrTiO3 substrate, there is also a phase transition with the increasing layer thickness n. The polarization increases with strain or layer thickness. The ferroelectric properties and size effect in the free standing RP phase SnO(SnTiO3)n nanosheets were also investigated, and the in-plane polarization is 60% larger than that of the bulk.